<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
  <style>
  
      .item{
        position:fixed;
        width:100px;
        height:100px;
        left:0;
        top:0;
        background-color: #f00;
        
      }
      .box2{
        left:20px;
        top:20px;
        background-color: #0f0;
        z-index: -1;
      }
      .box3{
        left:40px;
        top:40px;
        background-color: #00f;
      }
      .info{
        position:absolute;
        z-index: 999;
      }
      
      </style>
</head>
<body>
   
      </head>
      <body>
        <div class="item box1">1</div>
        <div class="container">
            <div class="item box2">2
              <div class="info">哈哈哈</div>
            </div>
        </div>
       
        <div class="item box3">3</div> 


</body>
</html>